1. Field of the Invention
The present invention relates to an aqueous ink containing water, a water-soluble organic solvent, and a colorant. More specifically, the present invention relates to an aqueous ink suitable for an ink-jet recording method (image forming method or recording method) or for an ink-jet recording apparatus, and to an ink-jet recording method, ink-jet recording apparatus, and image forming method using the same.
2. Related Background Art
Ink containing a pigment as a colorant (pigment ink) has been conventionally known to provide an image excellent in color-fastness such as water resistance or light resistance. Various techniques have been proposed in recent years for further improving an optical density of an image formed by such ink and for more efficiently suppressing color mixing (bleeding) at a boundary portion between respective color images when recording a color image in which areas of different colors are adjacent to each other.
For example, there has been proposed a technique in which ink containing self-dispersible carbon black and a specific salt is used to further improve an image density (see, for instance, JP 2000-198955 A). There has been also proposed a technique in which ink for ink-jet recording, which is a composition containing a pigment, a polymer fine particle, a water-soluble organic solvent, and water, and a polyvalent-metal-salt-containing aqueous solution are allowed to adhere to a recording medium, and the ink composition and the polyvalent-metal-salt-containing aqueous solution are reacted to form a high-quality image (see, for instance, JP 2000-063719 A).
In each of those techniques, pigments dispersed in the ink are forced to aggregate on the surface of the recording medium to suppress permeation of the pigments into the recording medium, thereby resulting in an image having a higher density and suppressed bleeding as compared to an image provided by the conventional pigment ink.
As described above, in forming a high-quality image having a high density and suppressed bleeding, methods have been mainly utilized, which include a method involving separately incorporating a compound into ink and a method involving the reaction between two or more kinds of liquids.
However, ink components are preferably simplified. It has been generally desired to form a high-quality image comparable to that described above by appropriately designing basic components constituting an aqueous ink such as a colorant and a water-soluble organic solvent, and by controlling the combinations and the like of the basic components.